The objective of this project is to determine if abnormalities in the renin-angiotensin-aldosterone axis in patients with low-renin essential hypertension are compensatory, appropriate changes. The aims are to determine if these patients' greater than normal plasma aldosterone responses to angiotensin II become normal after increasing their renin activity with diuretic treatment, and, if their blunted renin activity responses to beta-adrenergic stimulation become normal after diuretic treatment.